Ferrovie dello Stato 2-8-2 Locomotives in Italy

Class Gruppo 746 (Locobase 2506)

Data from the US Military Railway Service's Equipment Data Book for Italian Locomotives supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "2-8-2 Express and 4-8-0 Compound Goods Locomotives: Italian State Railways", Locomotive Magazine, Volume XXVII [27] (15 July 1921), p. 171; "Four-Cylinder Compund Locomotive, Italian State Railways", Locomotive Magazine, No 368 (14 April 1923), pp. 98-99; and Wikipedia's "FS Class 746" entry at [], last accessed 23 February 2021.

Ugo Poddine, in his contribution to Bryan Attewell ([] Steam simulation (April 2000), notes that these Mikes were built for fast train service on all of the main lines. These included Milan to Rome and Milan to Venice as well as along the Adriatic coast.

Note that this was a very unusual service for a 2-8-2 wheel arrangement. When delivered, the design rolled on tall drivers. Wikipedia explained that using four drivers would spread the weight and allow good, if not equally fast, running.

LM's 1923 report commented on the "quite novel" valve gear, which was actuated by one set of valve gear on each side. High-pressure valves measured 265 mm (10.43") in diameter and provided inside admission. The larger 350 mm (13.78") valves supplying steam to the low-pressure cylinders were set up for outside admission. Moreover, both valves were housed in a single steam chest. Two multiple valves set below each cylinder combined "the functions of purger, relief valves, and anti-compressors."

NB: The heating surface area used by the Ferro Stato in their specs was based on the tubes' and flues' internal diameters. Thus the tube and flue heating surface measured 219.9 sq m (2,368 sq ft) and with the firebox, 237 sq m (2,551 sq ft). Locobase uses the external (water side) diameter.

They generated 1,750 hp at 50 mph (81 kph), according to Poddine, who numbers 60 engines in the class. The first 50 had Walschaert's gear, the last 10 Caprotti. Wikipedia's entry says that " The locomotives fitted with Caprotti valve gear ...turned out to have problems when functioning in reverse."Gruppo 746 boilers were rated at 27,000 lb (12,075 kg) of steam per hour; horsepower rating was 1,600 at 45 mph (72.5 kph).

Wikipedia reports that "While fast, powerful and suitable for both fast passenger and goods trains, the Class 746 proved difficult to start and somewhat uneasy when running at or close to its top speed (with both problems originating from its compound engine); also, at higher speeds the low-pressure cylinders contributed relatively little to the locomotive's power output.

The engine's considerable size (it was the largest steam design to run on the FS) inspired the nickname "Krasin". (Wikipedia says the Krassin was a Soviet icebreaker that rescued Umberto Nobile. Nobile had flown the airship Norge over the polar ice cap--"Rome to Nome" in 1926 but crashed in 1928 in a later design named Italia. Wikipedia added the 746's rough ride led to the observation that just as the Krasin could break ice, the 746s could break rails.

Four were transformed into four-cylinder simple engines that appear in Locobase 3683. The others had already been retrofitted with the boiler used in the Grupo 691 Pacifics; those dimensions are also shown in the 746.026 entry.

Class Gruppo 746.046 (Locobase 3683)

Ugo Poddine, in his contribution to Bryan Attewell ([] Steam simulation (April 2000), says four of the 746 class of Mikados (Locobase 2506) were converted to a four-cylinder simple-expansion layout as shown here. See also Nino Carbone, "Gr 746 FS" entry posted 25 April 2015 in the Italia - Locomotive a vapore forum on the Marklinfan Club Italia website at [], last accessed 15 July 2021.

Nino Carbone's excellent account (translated by Google) says that the first two locomotives modified in November-December 1931 were the 746.046 (originally a Breda machine with Walschaert gear) and the 746.108 (from Ansaldo with Caprotti gear.) Tested against the compound 746s, the pair proved able to haul the same amount of freight, but were better suited to fast trains. This result led to the conversion of the 746.007 (Walschaert) and 107 (Caprotti) in the summer of 1932.

Boiler pressure increased as did driver diameter. Although they were successful conversions, only the four were so treated because the FS was preparing to electrify large portions of the system.

Class Gruppo 940 (Locobase 3690)

Data from Ugo Poddine as contributor to Bryan Attewell ([] Steam locomotive simulator (April 2000). Additional data from the US Military Railway Service's Equipment Data Book for Italian Locomotives supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Tank versions of the Grupo 740 Consolidations, these engines hauled mixed traffic through the mountains. It was credited by the MRS with 17,820 lb of steam per hour and rated at 980 hp at 27 mph.